Sediment records of the metal pollution at Chihu Lake near a copper mine at the middle Yangtze River in China

Two short sedimentary cores were collected in 2012 from Chihu Lake in the middle Yangtze River Basin using a gravity corer. Heavy metals, including Pb, Cu, Zn, Cd, Cr, Co, Ni and Mn, and major elements, including Al, Fe, K, Mg and Ti, were measured. Radionuclides, including 210Pb and 137Cs, were analyzed to date the sediments. The Mn enrichment in the sediments of the two cores did not significantly influence the distribution of the heavy metals. The Pb, Cu, Zn, Cd, Co and Ni contents have increased over the past 30 to 40 years. The decrease in the 206Pb/207Pb ratios toward the surface also indicated increasing mining sources of Pb loading to the lake sediments. The maximum concentration of Cu, Zn and Cd recorded in the 1990s was 2047, 1343 and 60.9 mg kg-1 dry mass, respectively, and the maximum enrichment factors of Cu, Zn and Cd were 62, 16 and 206, respectively. The heavy metal enrichment at Chihu sediment was high overall because of the mining waste discharge.